1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a method for controlling an amount of liquid crystal in an LCD device manufactured by a liquid crystal dispensing method.
2. Discussion of the Related Art
Among various ultra-thin flat type display devices, which include a display screen having a thickness of several centimeters, a liquid crystal display (LCD) device can be widely used in notebook computers, monitors, aircraft, and etc. since it has advantages such as low power consumption and portability.
Hereinafter, an LCD device according to the related art will be explained as follows.
FIG. 1 illustrates an exploded perspective view of an LCD device according to the related art.
As shown in FIG. 1, an LCD device according to the related art includes a lower substrate 10, an upper substrate 20, and a liquid crystal layer (not shown) formed between the lower and upper substrates 10 and 20.
The lower substrate 10 includes gate and data lines 12 and 14 crossing each other to define a unit pixel region. Then, a thin film transistor TFT is formed adjacent to a crossing portion of the gate and data lines 12 and 14, wherein the thin film transistors TFT functions as a switch. Also, a pixel electrode 16 is formed in the pixel region, wherein the pixel electrode 16 is connected with the thin film transistor TFT.
The upper substrate 20 includes a black matrix layer 22 for preventing light leakage from other portions except the pixel region, a color filter layer 24 of red, green and blue patterns for representing colors in the portion corresponding to the pixel region, and a common electrode 26 formed on the color filter layer 24.
The LCD device is manufactured in steps including preparing the lower and upper substrates, and forming the liquid crystal layer between the lower and upper substrates. The liquid crystal layer may typically be formed using a dispensing method or a vacuum injection method.
In the vacuum injection method, a sealant having an inlet is formed in any one of the two substrates, and the two substrates are bonded to each other, and then liquid crystal is injected to a space between the two substrates.
In the dispensing method, a sealant having no inlet is formed in the lower substrate, and then liquid crystal is dispensed on the lower substrate. The two substrates are then bonded to each other.
As substrates increase in size, the vacuum injection method becomes problematic because it requires a long injection time, thereby lowering the production yield. Because of this, the large-sized LCD device generally uses the dispensing method.
However, the dispensing method of liquid crystal according to the related art has following disadvantages.
In the dispensing method of liquid crystal according to the related art, it is difficult to control an appropriate amount of liquid crystal.
Unlike the vacuum injection method, the dispensing method measures the appropriate amount of liquid crystal taking into consideration the size and height of cell. However, it is difficult to accurately control the amount of liquid crystal because of various environmental restrictions.
If the amount of liquid crystal is insufficient, the inside of an LCD panel is provided with incompletely-filled portions. Meanwhile, if the amount of liquid crystal is excessive, the inside of an LCD panel is provided with excessively-filled portions. As a result, a picture quality of displayed image is deteriorated.
Accordingly, extensive study and research have been made so as to prevent the liquid crystal from being provided insufficiently or excessively. If insufficiently or excessively dispensing the liquid crystal to the LCD panel, the LCD panel will have serious defects. Thus, even though it is costly and inefficient, LCD panels having insufficient or excessive liquid crystal are scrapped.